Air valve for stokers



Jan. 25, 1944. c. J. wlNKLER ETAL 2,340,281

AIR-VALVE FOR STOKERS YFiled sept. 21, 1940 INVENTORS. Cam. J, MNA/Ef? and Patented Jan. 25, 1944 z.s4o,2s1 Am VALVE Foa s'roxans cari J. Winklerand Herman E. Winkler, Lebanon, Ind., assignors to U. S. Machine Corporation, Lebanon, Ind., a corporation of Indiana Application September 21, 1940, Serial No. 357,690

9Clalms.

In the common form of small forced-draft stoker, it is customary to actuate simultaneously both the fuel-feeding mechanism and the blower which supplies the forced draft. One oi the disadvantages met with in the operation of such a stoker arises from the Sudden rush of air to the ilre when the blower is started. In the first place, such a sudden rush of air may create a positive pressure within the flre box and thus expel obnoxious gases and ilnely divided or ily ash from the ilre box through the flre door and other openings. In the second place, during intervals when the stoker is not operating, the ilre burns down and may become so low that it will be extinguished by the sudden rush of air which occurs when the blower is started.

It is the primary object of our invention to employ a common control for the fuel-feeding means and the blower which provides the forced draft but, at the same time, to so regulate the ow of air to the Stoker-retort that the supply of draft air will be built up gradually to its normal rate, thus eliminating a sudden blast of draft air and its consequent disadvantages as noted above. A further object of our invention is to control the quantity of air supplied to the flre under natural, or chimney, draft during periods in which the stoker is not operating. Still another object of our invention is to secure the results set forth by means of apparatus which can be economically manufactured and which can readily be installed in existing stokers.

In carrying out our invention in its preferred form, we mount in the air-supply conduit a valve secured to a shaft which extends outwardly through one wall of the conduit and which has secured to it one end of a spirally coiled bimetallic strip. The other end of this strip is anchored to a fixed point, and the strip is connected across the secondary of a transformer which is arranged to be energized simultaneously with an electric motor which operates the fuel-feeding mechanism and blower. The arrangement is such that when the bimetallic strip is cold the valve in the air supply conduit will be in or near closed position; but as the temperature of the bimetallic strip increases due to the passage of electric current through it it will rotate the valve-shaft and gradually open the valve, thus providing for a gradual increase in the supply of draft air and eliminating any sudden blast.

The accompanying drawing illustrates our invention: Fig. lis a vertical section on the line I--I of Fig. 2 illustrating the valve-controlling bimetallic strip and its associated parts in elevation; Fig. 2 is a vertical transverse section on the line 2-2 of Fig. l; Fig. 3 is a front elevation of the casing within .which the device is enclosed; and Fig. 4 is a side elevation of a complete stoker illustrating the manner in which our draft-control is installed in associaton therewith.

Referring to Fig. 4, the common form of stoker embodies a hopper I0, fuel-feeding means shown as comprising a feed tube II and a screw-conveyor I2 mounted therein, a blower I3, and a conduit I4 for conveying air from the blower to the retort (not shown) into which fuel from the tube II is fed.

In embodying our invention in association with a stoker, we mount in the air conduit I4 a valve I5 which regulates the quantity of air supplied to the retort from the blower I3. Conveniently, this valve is a balanced butterfly valve secured to a shaft I6 which projects horizontally through one side wall of the conduit into a casing comprising a base II and a removable cover I8. The cover I8 is removably held in place, as by means of screws 20 which project through holes or slots in the side walls of the cover and into ears 2l struck up from the casing-base Il. Within the casing I'I-IB, there is secured to the projecting end of the shaft I6 the inner end of a spirally coiled bimetallic strip 25, the outer end of which is secured to a bracket 26 mounted on a block 21 of electrical insulating material attached t'o the casing-base I'l in any convenient manner. A

second bracket 28 on the block 2l is electrically connected to the inner end of the bimetallic strip 25 by a flexible electrical conductor 29. The conductor 29 is desirably in the form of a flat braided copper cable spirally coiled and, while sufficiently flexible to accommodate rotation of the shaft IG through the opening and closing movement of the valve I5, suillciently rigid to insure that it will remain in spaced relation to the bimetallic strip 25.

The two brackets 26 and 28 are connected by wires 30 and 3| across the secondary of a stepdown transformer 32. The primary of the transformer 32 is connected in parallel with a motor 33 which operates the blower I3 and the fuel-feeding screw I2, the transformer and motor being under the common control of a single switch 34. Usually, the switch 34 will be a temperature-responsive switch responsive to the temperature of a room which the furnace is to heat.

As it may be desired at times to subject the valve I5 to manual control, we form the outer end of the shaft I6 into a crank 35 which projects through an arcuate slot Il in the front yall of the cover Il. auch slot being long enough to permit the valve to rotate from fully open to fully closed position.

If desired, wemay associate with the slot Il adjustable abutment: which limit the extent to which the valve IB is opened or closed.` The abutmenta illustrated in the drawing consist of ears il each of which is formed as the outwardly bent end of an arcuate strip Il of sheet-metal, the body of such strip being provided with an arcuate slot Il which receives a bolt 4I projecting -through the front wall of the cover Il. The two ears il project through the slot 38 on opposite sides of the crank It and therefore limit movement of the crank and, correspondingly, of the valve Il. By loosening the bolts t I the strips GI can be adjusted to bring the ears ll into any desired respective positions.

When the stoker is not operating to supply fuel to the retort, the switch Il is opened and no current is flowing through the bimetallic strip 2l. Accordingly, the temperature of the bimetallic strip is relatively low, and the valve I5 is closed. When the switch 34 is closed to operate the stoker, the transformer l2 is energized and current flows through the bimetallic strip 25.

Under the heating effect of this current, the temperature of the bimetallic strip increases and gradually rotates the shaft I8 to move the valve I5 toward open position. As a result, there is no sudden blast of air into the fire box and the pressure therein remains sub-atmospheric Vbecause of the natural draft through the chimney. In con-4 sequence, obnoxious gases and fly ash are not blown from the furnace into the surrounding space where their presence would obviously be objectionable.

Under certain conditions, it may not be desirable to have the valve I5 completely closed during intervals in which the stoker is not operating. Thus, the normal intensity of the natural draft, the burning characteristics of the fuel used, the design of the heating plant, and the nature of the heating load may be such as to make necessary or desirable a limited opening of the valve I5 during intervals when the stoker is not in operation in order to prevent extinguishment of the fire from lack of air or to insure the existence of at least a certain minimum heating effect.

Under these conditions, therefore, the strip 39*` at the right-hand (Fig. 3) end of the slot 36 may be adjusted inwardly along the slot to any desired extent so that it will engage the crank and prevent the bimetallic strip 25, when cold, from returning the valve I5 to completely closed position. The extent to which the valve opens when the bimetallic strip 25 is hot may be controlled by properly positioning the arcuate strip 39 at the opposite end of the slot 36. j

In order to prevent the bimetallic strip from becoming unduly stressed when holding the valve in open position, it is desirable to provide the casing II--I8 with an opening for the admission of air so as to further theradiation of heat from the bimetallic strip. Conveniently, such an opening, indicated at I5, is provided in the bottom wall of the cover Il. The opening 45 may also provide for passage of the wires 30 and 3i by which currentis supplied to the bimetallic strip, such wires being enclosed in a conduit 46 the end of which is secured through the medium of a suitable tting 41 to a bracket 48 disposed within the casing above the opening l5.

The rate at which the bimetallic strip operates to open the valve 'I5 when the blower is started dependa upon a number oi factors such as the electrical resistanceofthe bimetallic strip, the voltage impressed upon it, the extent to which it will be distorted as the result of temperature changes, and the rate at which heat is radiated from it. By suitable selection of these factors, it is possible to vary widely the rate at which the valve I5 opens. We find it desirable in most instances to construct the device so that complete opening of the valve will not occur until from one-half to two minutes after operation of the blower has been started. Gradual opening of the yalve during an interval of such extent will prevent the creation of positive pressures in the fire box and also will prevent the-'draft air from being supplied at a rateso high as might result in extinguishing a nre which has burned low during the preceding period in which the stoker was not operating.

We claim as our invention:

l. In combination with a stoker having a blower, fuel-feeding means. and a single electric motor for operating said blower and fuel-feeding means, a conduit for conveying draft air from said blowera valve in said conduit, a shaft rotatable to move said valve between open and closed positions, a spirally coiled bimetallio strip having one end secured to said shaft and thev other en'd secured to a ilxed point, said strip being arranged to rotate said shaft and thereby move said valve toward open position as the temperature of the strip increases, and a transformer having its primary connected in parallel with said motor and its secondary permanently connected to the end of said strip, whereby whenever said motor is operating said strip will receive current causing it to become heated and toopen said valve and maintain it open.

2. In combination with a stoker having a blower, fuel-feeding means, and a single electric motor for operating said blower and fuel-feeding means, a conduit for conveying draft air from said blower, a valve in said conduit, a shaft rotatable to move said valve between open and closed` positions, a spirally coiled bixnetallic strip having one end secured to said shaft and the other end secured to a fixed point, said strip being arranged to rotate said shaft and thereby move said valve toward open position as the temperature of the strip increases and capable of being heated by an electric current passing through it to a temperature at which it will move said valve to and maintain it in open position, and means for controlling the supply of electric current simultaneously to said motor and to said strip, whereby whenever said motor is operating said strip will receive current causing it to become heated and to open said valve and maintain it open.

3. In combination with a stoker having a blower, fuel-feeding means, and means including an electric motor for jointly operating said blower and fuel-feeding means, a conduit for conveying sition. and a means for controlling the supply of electric current simultaneously to said motor and to said strip, whereby whenever said motor is op erating said strip will receive current causing it to become heated and to open said valve and maintain it open.

4. The invention set forth in claim 3 with the addition of an adjustable stop for limiting closing movement of said valve.

5. A device for supplying draft air to a stoker, comprising a blower, an electric motor for operating said blower, a conduit for conveying draft air from said blower, a valve in saidconduit, a shaft rotatable to move said valve between open and closed positions, a spirally coiled bimetallicstrip having one end secured to said shaft and the other end secured to a fixed point, said strip being arranged to rotate said shaft and thereby move said valve toward open position as the temperature of the strip increases and capable of being heated by an electric current passing through it to a temperature at which it will move said valve to and maintain it in open position, and a means for controlling the supply of electric current simultaneously to said motor and to said strip, whereby whenever said motor is operating said strip will receive current causing it to become heated and to open said valve and maintain it open.

6. The .invention set forth in claim 5 with the addition of an adjustable stop for limiting closing movement of said valve.

'1. The invention set forth in claim 5 with the addition of adjustable stops for limiting opening and closing movements of said valve.

8. The invention set forth in claim 5 with the addition of a casing enclosing said strip, one wall of said casing having an arcuate slot concentricwith said shaft, said shaft being provided with a crank projecting outwardly through said slot, and stops disposed in said slot on opposite sides of said crank and adjustable along said slot to limit opening and closing movements of said valve.

9. The invention set forth in claim 5 with the addition of a casing enclosing said strip, one wall of said casing having an arcuate slot concentric with said shaft, said shaft being provided with a crank projecting outwardly through said slot.

CARL J. WINKLER.

CERTIFICATE oF CORRECTION; Patent No. 2,5 i1.0,281. January 25, 19h14..

CARI. J. wINxIER, El' AI..

I It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 56, `0I end read -endsg and that the said Letters Patent should be read with this correction therein that the same may con? fom to the record of the case in the Patent Office.

signed' and sealed this 5015.11 dy ofnay., A. D. 19ML.

Leslie', Frazer (S681) Acting Comnissioner of Patents. 

